diff --git a/zpa-core/src/main/kotlin/org/sonar/plsqlopen/symbols/DefaultTypeSolver.kt b/zpa-core/src/main/kotlin/org/sonar/plsqlopen/symbols/DefaultTypeSolver.kt
index 119b4b6a..a09b52c0 100644
--- a/zpa-core/src/main/kotlin/org/sonar/plsqlopen/symbols/DefaultTypeSolver.kt
+++ b/zpa-core/src/main/kotlin/org/sonar/plsqlopen/symbols/DefaultTypeSolver.kt
@@ -35,11 +35,11 @@ open class DefaultTypeSolver {
         } else if (node.type === PlSqlGrammar.LITERAL) {
             return solveLiteral(node)
         }
-        return UnknownDatatype()
+        return UnknownDatatype
     }
 
     open fun solveDatatype(node: AstNode, scope: Scope?): PlSqlDatatype {
-        var type: PlSqlDatatype = UnknownDatatype()
+        var type: PlSqlDatatype = UnknownDatatype
         if (node.hasDirectChildren(PlSqlGrammar.CHARACTER_DATAYPE)) {
             type = CharacterDatatype(node)
         } else if (node.hasDirectChildren(PlSqlGrammar.NUMERIC_DATATYPE)) {
@@ -59,13 +59,13 @@ open class DefaultTypeSolver {
             type = JsonDatatype()
         } else {
             val datatype = node.firstChild
-            type = scope?.getSymbol(datatype.tokenValue, Symbol.Kind.TYPE)?.datatype ?: UnknownDatatype()
+            type = scope?.getSymbol(datatype.tokenValue, Symbol.Kind.TYPE)?.datatype ?: UnknownDatatype
         }
         return type
     }
 
     open fun solveLiteral(node: AstNode): PlSqlDatatype {
-        var type: PlSqlDatatype = UnknownDatatype()
+        var type: PlSqlDatatype = UnknownDatatype
         if (node.hasDirectChildren(PlSqlGrammar.NULL_LITERAL) || isEmptyString(node)) {
             type = NullDatatype()
         } else if (node.hasDirectChildren(PlSqlGrammar.CHARACTER_LITERAL)) {
diff --git a/zpa-core/src/main/kotlin/org/sonar/plsqlopen/symbols/SymbolVisitor.kt b/zpa-core/src/main/kotlin/org/sonar/plsqlopen/symbols/SymbolVisitor.kt
index d9d07b1f..6e497df8 100644
--- a/zpa-core/src/main/kotlin/org/sonar/plsqlopen/symbols/SymbolVisitor.kt
+++ b/zpa-core/src/main/kotlin/org/sonar/plsqlopen/symbols/SymbolVisitor.kt
@@ -204,7 +204,7 @@ class SymbolVisitor(private val typeSolver: DefaultTypeSolver, private val globa
         }
 
         val datatype = node.getFirstChildOrNull(PlSqlKeyword.RETURN)?.nextSibling
-        val type = if (datatype != null) solveType(datatype) else UnknownDatatype()
+        val type = if (datatype != null) solveType(datatype) else UnknownDatatype
         val symbolKind = when(node.type) {
             PlSqlGrammar.CREATE_PROCEDURE -> Symbol.Kind.PROCEDURE
             PlSqlGrammar.PROCEDURE_DECLARATION -> Symbol.Kind.PROCEDURE
@@ -243,7 +243,7 @@ class SymbolVisitor(private val typeSolver: DefaultTypeSolver, private val globa
             }
             enterScope(node, autonomousTransaction = false, exceptionHandler = false)
         } else {
-            val symbol = createSymbol(identifier, Symbol.Kind.PACKAGE, UnknownDatatype())
+            val symbol = createSymbol(identifier, Symbol.Kind.PACKAGE, UnknownDatatype)
             enterScope(node, autonomousTransaction = false, exceptionHandler = false)
             symbol.innerScope = currentScope
         }
@@ -251,7 +251,7 @@ class SymbolVisitor(private val typeSolver: DefaultTypeSolver, private val globa
 
     private fun visitCursor(node: AstNode) {
         val identifier = node.getFirstChild(PlSqlGrammar.IDENTIFIER_NAME)
-        val symbol = createSymbol(identifier, Symbol.Kind.CURSOR, UnknownDatatype())
+        val symbol = createSymbol(identifier, Symbol.Kind.CURSOR, UnknownDatatype)
         enterScope(node)
         symbol.innerScope = currentScope
     }
@@ -275,7 +275,7 @@ class SymbolVisitor(private val typeSolver: DefaultTypeSolver, private val globa
                    control.hasDirectChildren(PlSqlGrammar.DYNAMIC_SQL)) {
             RowtypeDatatype()
         } else {
-            UnknownDatatype()
+            UnknownDatatype
         }
 
         for (declaration in declarations) {
diff --git a/zpa-core/src/main/kotlin/org/sonar/plugins/plsqlopen/api/squid/SemanticAstNode.kt b/zpa-core/src/main/kotlin/org/sonar/plugins/plsqlopen/api/squid/SemanticAstNode.kt
index c6f4ca75..39da3891 100644
--- a/zpa-core/src/main/kotlin/org/sonar/plugins/plsqlopen/api/squid/SemanticAstNode.kt
+++ b/zpa-core/src/main/kotlin/org/sonar/plugins/plsqlopen/api/squid/SemanticAstNode.kt
@@ -44,7 +44,7 @@ class SemanticAstNode(type: AstNodeType, name: String, token: Token?) : AstNode(
             (child as SemanticAstNode).symbol = symbol
         }
 
-    var plSqlDatatype: PlSqlDatatype = UnknownDatatype()
+    var plSqlDatatype: PlSqlDatatype = UnknownDatatype
         get() = this.symbol?.datatype ?: field
 
     val plSqlType: PlSqlType
diff --git a/zpa-core/src/main/kotlin/org/sonar/plugins/plsqlopen/api/symbols/Symbol.kt b/zpa-core/src/main/kotlin/org/sonar/plugins/plsqlopen/api/symbols/Symbol.kt
index 5a749df8..a8935670 100644
--- a/zpa-core/src/main/kotlin/org/sonar/plugins/plsqlopen/api/symbols/Symbol.kt
+++ b/zpa-core/src/main/kotlin/org/sonar/plugins/plsqlopen/api/symbols/Symbol.kt
@@ -50,7 +50,7 @@ open class Symbol(val node: AstNode?,
 
     val type: PlSqlType = datatype?.type ?: PlSqlType.UNKNOWN
 
-    val datatype: PlSqlDatatype = datatype ?: UnknownDatatype()
+    val datatype: PlSqlDatatype = datatype ?: UnknownDatatype
 
     val modifiers: List<AstNode>
         get() = Collections.unmodifiableList(internalModifiers)
diff --git a/zpa-core/src/main/kotlin/org/sonar/plugins/plsqlopen/api/symbols/datatype/UnknownDatatype.kt b/zpa-core/src/main/kotlin/org/sonar/plugins/plsqlopen/api/symbols/datatype/UnknownDatatype.kt
index e6cc8d90..8f1f44e8 100644
--- a/zpa-core/src/main/kotlin/org/sonar/plugins/plsqlopen/api/symbols/datatype/UnknownDatatype.kt
+++ b/zpa-core/src/main/kotlin/org/sonar/plugins/plsqlopen/api/symbols/datatype/UnknownDatatype.kt
@@ -21,7 +21,7 @@ package org.sonar.plugins.plsqlopen.api.symbols.datatype
 
 import org.sonar.plugins.plsqlopen.api.symbols.PlSqlType
 
-class UnknownDatatype : PlSqlDatatype {
+object UnknownDatatype : PlSqlDatatype {
     override val type = PlSqlType.UNKNOWN
 
     override val name: String? = null
diff --git a/zpa-core/src/test/kotlin/org/sonar/plsqlopen/symbols/SymbolTableImplTest.kt b/zpa-core/src/test/kotlin/org/sonar/plsqlopen/symbols/SymbolTableImplTest.kt
index b8019568..1bff928a 100644
--- a/zpa-core/src/test/kotlin/org/sonar/plsqlopen/symbols/SymbolTableImplTest.kt
+++ b/zpa-core/src/test/kotlin/org/sonar/plsqlopen/symbols/SymbolTableImplTest.kt
@@ -71,7 +71,7 @@ class SymbolTableImplTest {
         val scope = ScopeImpl(null, newAstNodeForTest("scope"), isAutonomousTransaction = false, hasExceptionHandler = false)
 
         val symbolTable = SymbolTableImpl()
-        val symbol = symbolTable.declareSymbol(node, Kind.CURSOR, scope, UnknownDatatype())
+        val symbol = symbolTable.declareSymbol(node, Kind.CURSOR, scope, UnknownDatatype)
 
         assertThat(symbolTable.symbols.find { it.declaration == node }).isEqualTo(symbol)
         assertThat(symbolTable.symbols.find { it.declaration == node2 }).isNull()
@@ -84,7 +84,7 @@ class SymbolTableImplTest {
         val scope = ScopeImpl(null, newAstNodeForTest("scope"), isAutonomousTransaction = false, hasExceptionHandler = false)
 
         val symbolTable = SymbolTableImpl()
-        symbolTable.declareSymbol(node, Kind.CURSOR, scope, UnknownDatatype())
+        symbolTable.declareSymbol(node, Kind.CURSOR, scope, UnknownDatatype)
 
         assertThat(symbolTable.symbols.find { it.declaration == node }?.scope).isEqualTo(scope)
         assertThat(symbolTable.symbols.find { it.declaration == node2 }?.scope).isNull()
@@ -97,8 +97,8 @@ class SymbolTableImplTest {
         val node = newAstNodeForTest("foo")
 
         val symbolTable = SymbolTableImpl()
-        val symbol1 = symbolTable.declareSymbol(node, Kind.CURSOR, scope, UnknownDatatype())
-        val symbol2 = symbolTable.declareSymbol(node, Kind.VARIABLE, scope, UnknownDatatype())
+        val symbol1 = symbolTable.declareSymbol(node, Kind.CURSOR, scope, UnknownDatatype)
+        val symbol2 = symbolTable.declareSymbol(node, Kind.VARIABLE, scope, UnknownDatatype)
 
         assertThat(symbolTable.symbols.filter { it.kind == Kind.CURSOR }).containsExactly(symbol1)
         assertThat(symbolTable.symbols.filter { it.kind == Kind.VARIABLE }).containsExactly(symbol2)
@@ -113,8 +113,8 @@ class SymbolTableImplTest {
         val node2 = newAstNodeForTest("FOO")
 
         val symbolTable = SymbolTableImpl()
-        val symbol1 = symbolTable.declareSymbol(node1, Kind.CURSOR, scope, UnknownDatatype())
-        val symbol2 = symbolTable.declareSymbol(node2, Kind.VARIABLE, scope, UnknownDatatype())
+        val symbol1 = symbolTable.declareSymbol(node1, Kind.CURSOR, scope, UnknownDatatype)
+        val symbol2 = symbolTable.declareSymbol(node2, Kind.VARIABLE, scope, UnknownDatatype)
 
         assertThat(symbolTable.symbols.filter { it.name.equals("foo", ignoreCase = true) }).containsExactly(symbol1, symbol2)
         assertThat(symbolTable.symbols.filter { it.name.equals("bar", ignoreCase = true) }).isEmpty()